OpenPop.NET 2.0.4 released

This release fixes some bugs regarding Received header lines.
Webpage has been update.
EncodingFinder class created to enable injection of custom Encodings.
More examples added to webpage.
Robustness of Rfc2231 decoding increased.

Note: Removes obsolete methods. Therefore this update is a breaking update (though very easy to fix, as just method names changed).